A study by Duke University and Boston University, released Jan. 16, 2014, finds nearly 5,900 natural gas pipeline leaks in Washington, D.C. Residents and tourists are shown near the city's Tidal Basin in April 2007. / Tim Dillon, USA TODAY

by Wendy Koch, USA TODAY

by Wendy Koch, USA TODAY

New research today says the nation's capital, notorious for leaking state secrets, has thousands of leaks of another sort: methane from natural gas pipelines.

More than 5,800 leaks from aging pipelines were found under Washington, D.C.'s streets by scientists from Duke University and Boston University, who dispatched a car equipped with measuring instruments across the city last January and February. Their findings appear in this week's peer-reviewed journal Environmental Science & Technology.

The researchers found 19 of the leaks had high concentrations of methane, a potent heat-trapping greenhouse gas that contributes to global warming as well as smog-forming ozone. So they got out of the car and put probes into manholes. They found 12 could have caused explosions because of their levels - up to 10 times the threshold at which explosions can occur.

In February, they reported the leaks to Washington Gas, the local utility, but upon follow-up testing four months later, found nine of them were still emitting dangerous levels of methane.

"If you dropped a cigarette down a manhole ... it could have blown up," says Robert Jackson, professor of environmental sciences at Duke who led the study. "I was shocked," he says, adding gas companies usually respond quickly to leaks for fear of negative publicity. Since some are limited in how much they can spend to fix pipes, he says the study may help them obtain money for repairs.

"Washington Gas immediately responds to every report of natural gas odor and repairs leaks 7 days a week, 24 hours a day, 365 days a year," Eric Grant, vice president of corporate relations, said in a statement, noting he has not yet reviewed the study. "With over 13,000 miles of distribution mains and more than 940,000 service lines in our system, it is not realistic to state that there are no leaks."

Betty Ann Kane, who chairs the D.C. Public Service Commission, said the study's findings could mistakenly alarm residents. She said the city does not have 5,000 dangerous gas leaks and has not had an accident or explosion from a pipeline leak in at least 20 years.

She says the commission ordered Washington Gas to do a $28 million, seven-year program to replace the connections between pipes - the company is now midway through it - and accelerate its replacement of cast iron pipes with PVC (polyvinyl chloride.)

Grant said all utilities are challenged by aging infrastructure, adding Maryland and Virginia are among three dozen states that have written laws to allow for its accelerated replacement.

Pipeline leaks are drawing more attention as natural gas production and use booms in the United States. The Duke and Boston researchers say these leaks are the nation's largest human-caused source of methane, contributing to the $3 billion of natural gas that's lost or unaccounted for each year.

"Climate-wise, it's potentially a big deal," Jackson says. Methane can trap more than 20 times as much heat in the atmosphere as carbon dioxide, but it dissipates much more quickly.

The researchers mapped gas leaks under the city's 1,500 road miles via a GPS-equipped car with a high-precision spectrometer. Their laboratory analyses found that the chemical makeup of the vast majority of methane leaked matched that of pipeline gas.

They began similar work in Boston in 2011, and found it had a similar number of leaks per mile as Washington, D.C., but at lower concentrations. They've since put instruments atop some of Boston's buildings, including the Prudential Tower, to measure methane in the atmosphere.

Jackson says they hope to do the same in the nation's capital although its buildings are shorter. He says both Boston and Washington, D.C., because they're older, are likely leakier than younger cities.